Transport of toluene/methyl ethyl ketone mixtures in polyisobutylene

In this study, the diffusion behavior of methyl ethyl ketone (MEK)/toluene mixtures, with MEK molar fractions (x₁) in the liquid source lower than 0.2, in polyisobutylene (PIB) was investigated with vapor‐sorption Fourier transform infrared attenuated total reflectance (FTIR‐ATR) spectroscopy. FTIR‐ATR Fickian diffusion models for both binary and ternary systems were used to determine diffusion coefficients. Obtained diffusion coefficients for MEK from the binary diffusion model did not agree with those determined previously for the diffusion of MEK/toluene mixtures, with x₁ > 0.2, in PIB. When the ternary diffusion model was used, the main‐term and cross‐term diffusion coefficients of MEK were comparable. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 908–914, 2001     

Compositional heterogeneity effects in multisticker associative polyelectrolytes prepared by micellar polymerization

An aqueous micellar radical polymerization technique has been used to prepare water‐soluble polyelectrolytes of acrylamide (AM) and sodium 2‐acrylamido‐2‐methylpropanesulfonate (NaAMPS) hydrophobically modified with low amounts (2–4 mol %) of N,N‐dihexylacrylamide (DiHexAM). This synthesis method leads to multisticker polymers, in which the number and length of the hydrophobic blocks vary with the degree of conversion. Kinetic studies show an appreciable compositional heterogeneity for these polymers, in contrast to their neutral analogues (i.e., AM/DiHexAM copolymers). The drift in composition observed for the AM/NaAMPS/DiHexAM terpolymers is attributed to the electrostatic repulsion between the negatively charged growing polymeric chains, located in the aqueous continuous medium, and the anionic sodium dodecyl sulfate micelles, inside of which the hydrophobic monomer is entrapped. It is shown that an optimization of the polymerization process can be achieved, which gives terpolymers of homogeneous and well‐defined compositions. The thickening ability of the hydrophobically modified polyelectrolytes is directly affected by the extent of their compositional heterogeneity: an increase in the sample homogeneity leads to a significant viscosity enhancement and marked elastic properties of the polymer solutions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3261–3274, 2003     

Hyperbranched fluorocopolymers by atom transfer radical self‐condensing vinyl copolymerization

Hyperbranched fluorocopolymers were synthesized by the atom transfer radical self‐condensing vinyl copolymerization (ATR–SCVCP) of an inimer, either p‐chloromethylstyrene (CMS) or p‐bromomethylstyrene (BMS), with 2,3,4,5,6‐pentafluorostyrene (PFS), with 2,2′‐bipyridine together with CuCl or CuBr as the ligand/catalyst system. The reaction conditions were studied to provide for control over the copolymer compositions, molecular weights, degrees of branching, and properties, as characterized by ¹H, ¹³C, and ¹⁹F NMR spectroscopy, gel permeation chromatography, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and solubility tests. Copolymers having number‐average molecular weights from 2.9 to 260 kDa and polydispersities (weight‐average molecular weight/number‐average molecular weight) from 1.8 to 4.8 were obtained. The molar fractions of PFS units increased with increases in the feed ratio of PFS to the inimer. The degrees of branching were typically about 30% with the feed of 1.0 or 2.0 equiv of PFS with respect to the inimer, although slight variations could be achieved through the variation of the inimer composition. Under similar reaction conditions with CuCl as the catalyst, ATR–SCVCP of BMS with PFS led to higher degrees of branching than ATR–SCVCP of CMS with PFS. Solubility tests indicated that the polymers prepared under conditions that avoided extensive biradical coupling were soluble in a broad range of organic solvents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4754–4770, 2005     

Samarium enolate on crosslinked polystyrene beads. II. An anionic initiator for the well‐defined synthesis of poly(allyl methacrylate) on a solid support

A samarium enolate, supported on a crosslinked polystyrene resin, successfully initiated the living anionic polymerization of allyl methacrylate (AMA) to afford the corresponding poly(AMA) with well‐controlled molecular weights. Diblock, triblock, and tetrablock copolymerizations with methyl methacrylate (MMA) were also successfully performed. The formed polymers, supported on the resin by a benzyl ester linker, were quantitatively isolated from the resin by selective cleavage of the linker with trifluoroacetic acid (TFA). Allyl ester in the side chain was not affected by this isolation step. The allyl group of the immobilized poly(AMA‐b‐MMA) on the resin was transformed into a 2,3‐dihydroxypropyl group by osmium oxidation. The resulting copolymer was isolated by TFA treatment of the resin, and it showed amphiphilicity. In both the polymerization and side‐chain modification, the formed polymers were easily washed from excess reagents only by filtration, and this demonstrated the feasibility of the automated synthesis of functional polymers based on this solid‐supported polymerization technique. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 853–860, 2003     

Living free‐radical polymerization (reversible addition–fragmentation chain transfer) of 6‐[4‐(4′‐methoxyphenyl)phenoxy]hexyl methacrylate: A route to architectural control of side‐chain liquid‐crystalline polymers

Side‐chain liquid‐crystalline polymers of 6‐[4‐(4′‐methoxyphenyl)phenoxy]hexyl methacrylate with controlled molecular weights and narrow polydispersities were prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization with 2‐(2‐cyanopropyl) dithiobenzoate as the RAFT agent. Differential scanning calorimetry studies showed that the polymers produced via the RAFT process had a narrower thermal stability range of the liquid‐crystalline mesophase than the polymers formed via conventional free‐radical polymerization. In addition, a chain length dependence of this stability range was found. The generated RAFT polymers displayed optical textures similar to those of polymers produced via conventional free‐radical polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2949–2963, 2003     

Linear soluble polybenzyls

Linear soluble polybenzyls, although deceptively simple in structure, have been strangely elusive. We report for the first time the synthesis of perfectly linear soluble polybenzyls by the polycondensation of 1,2,4,5‐tetrasubstituted benzenes with formaldehyde using CHCl₃/trifluoroacetic acid (TFA) as the medium, wherein TFA served both as an acidic catalyst as well as a cosolvent. The number‐average molecular weights (M_n's) of the polymers, as determined by gel permeation chromatography, varied from about 1000 to 37,000, depending on the nature of the substituent on the benzene ring; M_n was highest when all four substituents were alkoxy groups and was lowest when they were all alkyl groups. This correlated well with susceptibility of the aromatic ring toward electrophilic aromatic substitution, which is the underlying polymerization mechanism. Differential scanning calorimetry of the polymers showed that most of the samples were amorphous with glass‐transition temperatures ranging from about ?80° to +80 °C, whereas a few that were either symmetrically substituted or possessed a long alkyl substituent were partially crystalline. Preliminary studies suggested that the methylene unit linking the phenyl rings in these polybenzyls could be readily oxidized to generate conjugated polymers that may be perceived as carbon analogues of polyaniline–poly(arylmethine)s. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2345–2353, 2003     

Self‐diffusion of styrene, 2,2′‐azobisisobutyronitrile,and polystyrene in bulk polymerization by pulsed‐gradient spin‐echo nuclear magnetic resonance spectroscopy

The self‐diffusion of styrene, polystyrene, and 2,2′‐azobisisobutyronitrile has been determined in the bulk polymerization of styrene with pulsed‐gradient spin‐echo nuclear magnetic resonance at 25 °C. Data on small molecules are discussed with respect to recent diffusion models. They can fit self‐diffusion coefficient data of small molecules in dilute or semidilute polymer solutions; in concentrated solutions, however, there is a breakdown. A semiempirical model based on scaling laws is used to describe the self‐diffusion of styrene and 2,2′‐azobisisobutyronitrile over the whole range of concentrations studied. The dependence of the polystyrene self‐diffusion coefficient on the polymer concentration is described with a stretched exponential function, D = D₀ exp(?αc^ν), where α depends on the molecular weight of the polymer and ν depends on the kind of solvent. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1605–1614, 2003     

Characterization of large molecular weight ester‐functionalized norbornene and hydroxylated norbornane carboxylic acid polymers prepared by ring‐opening metathesis polymerization

5‐Norbornene‐2‐ethyl ester (mixture of endo and exo) is polymerized via ring‐opening metathesis polymerization, yielding polymers with molecular weights ranging from 50,000 to 5,000,000 g/mol. The polymers are hydroxylated and saponified without alteration of the molecular weight. The polymers are analyzed by NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. Films are cast from the polymers at several molecular weights and their rheological properties are investigated. The results showed greater solid‐like character with increasing molecular weight for all polymers analyzed. Cell viability studies showed that the films possessed minimal cytotoxicity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Study of the phase transition of poly(N,N‐diethylacrylamide) in water by rheology and dynamic light scattering

Poly(N,N‐diethylacrylamide) (PDEA) possesses a lower critical solution temperature (LCST) in aqueous media. The solution properties of PDEA at various temperatures have been characterized with techniques such as rheology and dynamic light scattering. There is a decrease in the coil size before the phase transition due to a coil‐to‐globule transition. At the LCST, rheological and dynamic light scattering studies have also confirmed an aggregation phenomenon. This aggregation modifies the rheological properties of the polymer solutions. High frequencies hinder the phase‐transition process and reduce the LCST of the polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1627–1637, 2003     

Method of determining the absolute molecular weight from gel permeation chromatograms for star‐shaped styrenic block copolymers

A gel permeation chromatography (GPC) calculation method has been developed to determine the absolute molecular weight of a star‐shaped styrenic block copolymer with GPC–ultraviolet/refractive index calibrated with linear polystyrene standards. To illustrate the simplicity of this method, we have synthesized nearly monodisperse, multiple‐arm model polymers either by linking living polymeric arms with multifunctional silicon halide or by oligomerizing the p‐chloromethylstyrene‐terminated polystyrene macromonomers. The good agreement between the absolute molecular weight determined with this calculation method and that actually measured with a multi‐angle laser light scattering device has corroborated the validity of the calculation method. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 976–983, 2003     

Highly stable rigid main‐chain nonlinear optical polymers with nematic phase: Effect of liquid‐crystalline phase on nonlinear optical response

Nonlinear optical (NLO) rigid main‐chain polyesters containing azobenzene mesogens with high thermal and temporal stabilities were synthesized from derivatives of hydroxyphenylazobenzoic acid. The NLO properties of the homopolymer, poly[4‐(4‐hydroxy‐3‐methyl phenyl)azo]benzoic acid, and copolymers of 4‐[(4‐hydroxy‐3‐methylphenyl)azo]benzoic acid, 4‐[(4‐hydroxy‐2‐methylphenyl)azo]benzoic acid, and 4‐[(4‐hydroxy‐2‐pentadecyl phenyl)azo]benzoic acid (PSCpHBA) with p‐HBA were measured by the Maker fringe technique. The thermal and liquid‐crystalline (LC) phase behaviors of the polymers were examined by differential scanning calorimetry, a thermal‐stimulated polarization current, and polarized light microscopy. The polymers except PSCpHBA exhibited nematic‐threaded and Schlieren textures. The LC orientations give rise to an enhanced NLO response. The polymers had high thermal and temporal stabilities for second‐harmonic generation activity because of their rigid aromatic backbone. This study suggests that the rigid aromatic main chain exhibiting an LC phase is a promising simple method to synthesize highly stable NLO polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1527–1535, 2003     

Stability of polyaniline in air and acidic water

Polyaniline is a member of the class of electrically conducting polymers, having possible commercial applications such as coatings. Aqueous‐based polyaniline coatings are preferred over organic solvent or concentrated strong acid based coatings because water is not a pollutant. The overall goal of this study was to further the development of water‐based polyaniline coatings by an examination of the effect of acidic water (pH 1.18) and air on polyaniline. Knowledge of the effect of water on the structure, molecular weight, electrical conductivity, and diffusion of the dopant assisted in ascertaining whether polyaniline degraded with water exposure. Knowledge of how Fourier transform infrared (FTIR) spectra would be affected by dry air was important for determining if polyaniline was chemically stable with time. The results showed that the molecular weight, ultraviolet–visible and FTIR spectra, and carbon‐to‐nitrogen molar ratio in the polymer backbone all remained unchanged during acidic water immersion. The constant nature of these physical parameters showed a high degree of water stability. A chloride ion diffusion coefficient of 2.8 to 85 × 10^?9 cm²/h, the chloride concentration, and the electrical conductivity were also measured with the water immersion time. Aging polyaniline powders in a desiccator for 5 years showed no effect on the molecular structure, as indicated by the FTIR spectrum. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 807–822, 2003     

Synthesis and properties of new ultraviolet–blue‐emissive fluorene‐based aromatic polyoxadiazoles with confinement moieties

Three families of fluorene–oxadiazole‐based polymers with confinement moieties have successfully been prepared by the two‐step method for polyoxadiazole synthesis. These polymers show good solubility in common organic solvents, high thermal stability, and strong violet and blue photoluminescence in solution and as films, respectively. Their low‐lying highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels originate from the electron deficiency of an oxadiazole moiety, and this suggests that they may be useful for blue‐emitting and electron‐transport/hole‐blocking layers in electroluminescent devices. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 674–683, 2003     

A detailed surface analytical study of degradation processes in (meth)acrylic polymers

The present study investigates the degradation behavior of various high‐molecular‐weight acrylic polymers (50,000 < M_n/g mol^?1 < 100,000), namely poly(methyl methacrylate) (PMMA), poly(n‐butyl methacrylate) (PBMA), poly(n‐butyl acrylate) (PBA), and poly(lauryl methacrylate) (PLMA), under extreme environmental conditions. These polymers were synthesized via various polymerization techniques to create different end‐groups. The polymers chosen are readily applicable in the formulation of surface coatings and were degraded under conditions which replicate the harsh Australian climate, where surface coatings may reach temperatures of up to 95 °C and are exposed to broad‐spectrum UV radiation of up to 1 kW m^?2. The degradation behavior of the polymeric materials on their surface was followed via ATR‐IR spectroscopy, high resolution FTIR microscopy, and X‐ray photoelectron spectroscopy. The extent of the observed thermal and photo‐oxidation is directly related to the length of the ester side group, with the degradation susceptibility decreasing in the order of PLMA > PBMA/PBA > PMMA, with PMMA still stable even after 5 months exposure to the harshest condition used (UV light at 95 °C). The general degradation mechanism involves the loss of the ester side groups to form methacrylic acid followed by cross‐linking. The effect of the variable end groups was found to be minimal. The results from this study are in good agreement with previous studies of low‐molecular‐weight model polymers under identical conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Dynamic evolution of gases in the γ‐ and helium‐ion radiolyses of solid polymers

The dynamic evolution of gaseous hydrogen, methane, and carbon dioxide in the γ‐ and ⁴He‐ion radiolyses of solid polymers was investigated. The polymers used include low‐density and high‐density polyethylene, polypropylene, polystyrene, poly(methyl methacrylate), Nylon 11, Nylon 6, and poly(dimer acid‐co‐alkyl polyamine). An inline quadrupole mass spectrometer was utilized to monitor the dynamic profiles of the gases produced in the radiolysis. One‐ and two‐dimensional numerical diffusion models were developed to simulate and extract optimum diffusion coefficients and gas yields from the experimental dynamic gas profiles. It was found that the dynamic evolution of molecular hydrogen from the bulk polymer is controlled by its diffusion in most cases, such as CO₂ in poly(methyl methacrylate). In the γ radiolysis of some polymers such as low‐density polyethylene and polypropylene, the dynamic evolution of methane is only partially controlled by the diffusion process, and some other postirradiation process is a factor. It is concluded that the simulation method developed in this article is helpful in understanding and predicting the mechanisms of gas evolution in the radiolysis of solid polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1449–1459, 2001     

Synthesis of well‐defined macromonomers and comb copolymers from polymers made by atom transfer radical polymerization

Poly(n‐butyl acrylate) macromonomers with predetermined molecular weights (1300 < number‐average molecular weight < 23,000) and low polydispersity indices (<1.2) were synthesized from bromine‐terminated atom transfer radical polymerization polymers via end‐group substitution with acrylic acid and methacrylic acid. These macromonomers, having a high degree of end‐group functionalization (>90%), were radically homopolymerized to obtain comb polymers. A high macromonomer concentration, combined with a low radical flux, was needed to obtain a high conversion of the macromonomers and a reasonable degree of polymerization. By the traditional radical copolymerization of the hydrophobic macromonomers with the hydrophilic monomer N,N‐dimethylaminoethyl methacrylate (DMAEMA), amphiphilic comb copolymers were obtained. The conversions of the macromonomers and comonomer were almost quantitative under optimized reaction conditions. The molecular weights were high (number‐average molecular weight ≈70,000), and the molecular weight distribution was broad (polydispersity index ≈ 3.5). Kinetic measurements showed simultaneous decreases in the macromonomer and DMAEMA concentrations, indicating a relatively homogeneous composition of the comb copolymers over the whole molecular weight range. This was supported by preparative size exclusion chromatography. The copolymerization of poly(n‐butyl acrylate) macromonomers with other hydrophilic monomers such as acrylic acid or N,N‐dimethylacrylamide gave comb copolymers with multimodal molecular weight distributions in size exclusion chromatography and extremely high apparent molecular weights. Dynamic light scattering showed a heterogeneous composition consisting of small (6–9 nm) and large (23–143 nm) particles, probably micelles or other type of aggregates. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3425–3439, 2003     

Unsaturated alkoxy‐substituted poly(p‐phenylene 1,3,4‐oxadiazole)s: Synthesis and chemical–physical characterization

A new series of alkoxy‐substituted poly(p‐phenylene 1,3,4‐oxadiazole)s modified by the insertion of small percentages of various comonomers were synthesized through the precursor polyhydrazides. The comonomers used contained trans double bonds or meta‐alkoxy‐substituted aromatic rings to improve the solubility of the final polymers. The synthesized copolymers were chemically characterized by ¹H NMR and Fourier transform infrared spectroscopy. In some cases, the copolymers really showed improved solubility in organic solvents. The ¹⁵N solid‐state NMR technique was applied to examine the degree of conversion from the precursor polyhydrazides to the final polymers, which determined the effective conjugated length in the target polyoxadiazoles. Thermal stability and structural characteristics of all the polymers as well as a preliminary investigation on the optical properties of polyoxadiazoles are also reported. The copolymers retained high absorbance in the UV region and high transmission in the whole telecommunication range. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3916–3928, 2003     

Unimodal molecular weight distribution of commercial polymers from viscoelastic data

This article presents a method that provides the molecular weight distribution (MWD) of polymeric material from rheological data. The technique has been developed to deal with linear polymers with a log‐normal molecular weight distribution. The rheological data must include the shear storage modulus, G′(ω), and the shear loss modulus, G″ (ω), ranging from the terminal zone to the rubberlike zone. It was not necessary to achieve the relaxation spectrums via the extremely unstable problem of inverting integral equations. The method has been tested with different polymers (polydimethylsiloxane, polyisoprene, random copolymer of ethylene and propylene, and polystyrene) and the calculated MWDs were in good agreement with experimental data. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1539–1546, 2000     

Nanoscale structure–property relationships in conjugated polymers: Implications for present and future device applications

The most prevalent molecular level structures and structure–property relationships for three basic classes of conjugated polymers are summarized. This discussion encompasses linear unsubstituted conducting polymers and those containing linear side‐chain and branched side‐chain substituents. The impact of these structural attributes on charge transport and photophysics is emphasized. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2630–2648, 2003     

Fourier transform infrared study on the sorption of water to various kinds of polymer thin films

The state of sorbed water and the sorbing processes of water to various polymer thin films were studied with Fourier transform infrared (FTIR) spectroscopy. To prepare the polymer films, we used poly(ethylene glycol)s of different molecular weights and various kinds of vinyl polymers, such as poly(2‐methoxyethyl acrylate). The O? H stretching band of water sorbed in the films increased gradually on contact with water vapor at 50% relative humidity and leveled off. When O? H stretching bands of water sorbed to polymer films were compared, the peak positions and profiles of water sorbed to the polymeric materials with the same hydrogen‐bonding site were similar. A hybrid density‐functional method supported the assignment of the peaks. Furthermore, the diffusion coefficient (D) of water vapor in the polymer films was estimated by time‐resolved measurements of the sorbed water at the very initial stage (0–830 s). It was clearly shown that the D values of water vapor in the polymer materials with a strong hydrogen‐bonding site were smaller than those in hydrophobic polymers. The usefulness of the FTIR technique to investigate water sorption to polymer materials was definitely demonstrated. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2175–2182, 2001